X-ray tube



A ril w, 192%.

M. MORRESON X-RAY TUBE Filed Sept. 22. 1925 INVENTOR ntfond MorrisonATTOIVQNEY Patented Apr. 10, 1928.

UNITED STATES PATENT OFFICE.

MONTFOR'D MORRISON, OF CHICAGO, ILLINOIS.

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Application filed September 22, 1925. Serial No. 67,885.

476,155 filed June 9, 1921 and Serial No.

684,336 filed January 4, 1924.

It is an object of my invention to provide an X-ray tube adapted for allkinds of m diography.

A further object is the provision of an X-ray tube which is simple indesign and may be easily manufactured.

A further object of my invention is to provide an X-ray tube of suchdesign that the liberation of gas during the operation of the tube willnot increase the gas pressure within the same to such an extent as tomaterially afiect the operation thereof.

A still further object of my invention is to provide an X-ray tubeadapted to operate at substantial gas pressures but which is providedwith a volumetric chamber whereby the operation of the tube is notimpaired as a 'result of gas liberation.

A still further object of the invention is to provide an X-ray tubehaving a unitary support for the cathode and anode and which is alsoprovided with a volumetric chamber surrounding these elements.

Further objects of the invention will become apparent as the descriptionis read.

The invention will be better understood by reference to the accompanyingdrawing, in which a longitudinal sectional view of an X-ray tubeembodying my invention is illustrated.

Referring to the drawing, the X-ray tube comprising my invention mayconsist of an insulating bushing or sleeve 2 made of any suitablematerial such as silica glass and the like. Disposed within the bushingis an anode 3 comprising a rod 4 of coppen or other good heat conductingmaterial having the target end 5 rounded. Centrally disposed within therounded end is a target 6 of tungsten, thorium or other suitableray-radiating material of high atomic weight. The intermediate portion 7of the anode is engaged by an interiorly extending annular flange 8secured to the bushing 2, the fit-being such as to permit the rod toexpand without plae'ingany strain upon the glass bushing.

The rod 4 is firmly securcd in position within the bushing 2 by theplatinum or, chrome-lron collar 9 which may be welded or otherwisehermetically sealed at 11 to the rod and also sealed at 12 to areentrant tube 13. The outer end 14 of the anode rod or shank may have asuitable radiator 15 secured thereto in any desirable manner.

The inner end 16 of the insulating bushing is substantially closed by awall 17 having an inner concave surface 18 conforming substantially tothe curvature of the rounded end 5 of the anode. An opening 19 in thewall 17 is arranged in axial alignment with the longitudinal axis of theanode, and within this.

opening is mounted a filamentary cathode 21 in the form of an openspiral. The center of the opening in the cathode lies in an extension ofthe longitudinal axis of the anode so that electrons emitted by thecathode will strike the target 6 at substantially right angles to thesurface thereof so that the X- rays generated thereby will pass alongthe longitudinal axis of the anode shank outwardly from the target andthrough the opening in the filamentary cathode 21.

It will be noted that the spacing 22 between the anode 3 and the innerwall 23 of the bushing 2 is very close and also that the space 24between the end 5 of the anode and the filamentary cathode 21- is alsovery close. The purpose of such close spacing, is to reduce to a minimumthe amount of gas ionization which may arise through electronic impactof. the gas molecules disposed within. this space. Preferably thisspacing should be such that it corresponds to the mean free path of themolecules of gas. In addition the surface of-the wall 23 of the bushingshould be of such order of magnitude that no leakage of current occursbetween the cathode and the anode.

Suitable leading-in conductors 25 and 26 connected to thefilamentarycathode 21 may be employed to conduct current thereto.

plished by the insulating bushim '2,

sealing at 33 a. spherical bulb of glass 34 to the insulating bushing 2.The size of the chamber 32 should be such that the liberation of gasduring the operation of the tube will not change the total pressuresufliciently to materially affect the operation of the tube, it beingappreciated that the present device is adapted to operate at substantialgas pressures of the order of 1 micron without detrimental gasionization occurring.

However, if desired,-the opening 19 ma be provided with a window (notshowng transparent to X-rays and which is gas tight. Such a window maybe made of glass sealed to the insulating bushing 2. The chamber 32 maybe evacuated by suitable connection at 35 and a residual gas pressure ofabout 1 micron left remaining or if desired a pure inert gas such ashydrogen. helium, neon, may be introduced within the chamber beforetipping-off.

The focussing of the electrons is accorlng t is curved surface 18 ofwhich becoming negatively charged during the operation of the tube andthus causing the electron stream to concentrate upon the target 16. Thewall 17 of the insulating bushing also functions to repress inverseelectron flow from the anode 4 and to serve as a screen for undesirableX-radiation.

The operation of the device is obvious from the preceding description.

Modifications of my invention will sugstthemselves to those skilled inthe art,

at such modifications are contemplated as coming within the spirit andscope of the appended claims.

What is claimed is:

1. An X-ray tube comprising a bulbous vessel, an insulating bushingsealed therethrough, an anode disposed within said bushing and spacedclosely from the inner wall thereof and a cathodesupported by saidbushing and spaced closely from said anode.

2. An X-ray tube comprising an insulat ing sleeve, an anode havlngatarget in one end disposed in said sleeve, means for hermeticallysealing said anode within said sleeve, a cathode supported by saidsleeve and disposed adjacent said'anode, said sleeve being substantiallyclosed at the' end in which said cathode is supported but having anopening through which X-rays may be emitted.

3. An X-ray tube comprising an insulating sleeve having a wall with anopening therethrough at one end thereof, a cathode within said opening,an anode within said sleeve and having the target end thereof disposedadjacent the opening, means for sealing said anode to said sleeve, andmeans closing said opening from the atmosphere.

4. An X-ray tube comprising an insulatof said sleeve in which thepassageway is positioned.

5. An X-ray tube comprising an insulating sleeve, an anode and a cathodesupported thereby, and a volumetric chamber enclosing one end of saidsleeve.

6. An X-ray tube comprising an insulating sleeve, an anode and a cathodesupported thereby, said anode having its target end positioned closelyadjacent said cathode, the anode and cathode being in alignment with thelongitudinal axis of said sleeve, said sleeve having an opening thereinfor the passage of X-rays, the opening also being in alignment with thelongitudinal axis .said sleeve and means for hermetically sealin" saidsleeve from the atmosphere.

' An X-ray tube comprising an insulat-' ing sleeve, arod of good heatconductin material sealed to said sleeve at one en the other end of saidsleeve having a closure wall with an opening therethrou h, a targetdisposed in the end of said 1'0 and adjacent the opening, said rod beingclosely spaced from said sleeve, a cathode disposed in the opening, saidrod, sleeve, target, opening and cathode being in longitudinalalignment, and means closing said opening from the atmosphere.

8. An X-ray tube comprising a spherical envelope, an insulating bushingsealed therein with one end projecting within said envelope and theother end extending without said envelope, an anode disposed within saidbushing and sealed thereto, said anode extending to a point adjacent theinner end of said bushing, the inner end of said sleeve having anopening, a thermionic cathode within the opening, and an inert gas at asubstantial pressure within said envelope, the size of said envelopebeing such that Ill any liberation of gas during operation of I the tubewill not change the total pressure within the tube to such an extent ,asto materially affect the operation thereof.

9. An X-ray tube comprising an elongated rod of good heat conductingmaterial, a sleeve of insulating material surrounding one end of saidrod and sealed at one end thereto, the spacing of said rod from thewalls of said sleeve being relatively close, said sleeve having a wallwith an opening therein, a cathode mounted in the openin and spacedclosely to the end of said ro means for sealing said opening from theatmosphere, the space within said sleeve being filled with an inert gasat a substantial pressure, and a target mounted in the end of said rod,whereby said tube may be operated at normal voltages and current withoutdetrimental gas ionization.

10. An X-ray tube comprising a hollow elongated vessel of goodinsulating material, an anode sealed at one end of said vessel andconcentrically disposed with respect thereto, the other end of saidanode having a target of good ray radiating material mounted therein, awall of insulating material closing one end of said vessel, said wallhaving an aperture therein, a cathode disposed in the aperture, saidanode, cathode and vessel being spaced in such relation as to permit theoperation of said device at normalvoltage and current in the presenceof'a substantial gas pressure but without detrimental gas ionization,and a filling of inert gas at about 1 micron pressure within saidvessel.

In testimony whereof, I have hereunto subscribed my name this 18th daySeptember, 1925.

MONTFORD MORRISON.

